To improve the diagnosis of cancer and other disorders, some researchers have used the systemic administration of imaging agents (e.g., proton relaxation agents as well as fluorescent chromophores) for contrast enhancement in techniques such as magnetic resonance imaging (MRI) and laser phototherapy. For example, tumor location using radiolabeled antibodies and handheld probes for intraoperative tumor detection has been attempted (Arnold et al., Surgery 112:624-631, 1992). Introduction of fluorescein conjugated antibodies for endoscopic tumor location ("photo-immunodiagnosis") in animals and in humans has also been attempted (Folli et al., Cancer Res. 54:2643-2450, 1994; Pelegrin et al., Cancer 67:2529-2535, 1994). In addition, fluorochrome-conjugated antibodies have been used to study antibody circulation in tumor microvasculature and biodistribution in tumors.
While such techniques show promise, their use has been limited by a lack of agents or conjugates that show specific localization to particular cell types. For example, localization to cell populations that are frequent sites of neoplastic development would aid in the diagnosis of incipient tumors. Further selectivity for neoplastic cells or macroscopic tumors would greatly aid in their localization and excision.
The ability to target imaging compounds to epithelial cells would enhance a variety of diagnoses, since such cells give rise to a wide spectrum of tumors, as well as viral and bacterial infections. Targeting of imaging compounds to epithelial cells would ideally delineate normal tissue from neoplastic lesions and potentially identify other types of lesions such as infections. Refinement of cell type specificity to be selective for the abnormal cells would further aid in localizing and treating those cells. However, no techniques are currently available for such targeting of imaging agents.
Accordingly, there remains a need in the art for systems for delivering imaging agents to target cells, particularly epithelial cells and cells or tissues bounded by epithelial cells. The present invention fulfills these needs and further provides other related advantages.